title: Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials.
abstract: BACKGROUND
  The results of studies investigating the effect of green tea on glucose control and insulin sensitivity in humans are inconsistent.
  
  
  OBJECTIVE
  We aimed to quantitatively evaluate the effect of green tea on glucose control and insulin sensitivity.
  
  
  METHODS
  We performed a strategic literature search of PubMed, EMBASE, and the Cochrane Library (updated to January 2013) for randomized controlled trials that evaluated the effects of green tea and green tea extract on glucose control and insulin sensitivity. Study quality was assessed by using the Jadad scale. Weighted mean differences were calculated for net changes in glycemic measures by using fixed-effects or random-effects models. We conducted prespecified subgroup and sensitivity analyses to explore potential heterogeneity. Meta-regression analyses were conducted to investigate dose effects of green tea on fasting glucose and insulin concentrations.
  
  
  RESULTS
  Seventeen trials comprising a total of 1133 subjects were included in the current meta-analysis. Green tea consumption significantly reduced the fasting glucose and hemoglobin A1c (Hb A1c) concentrations by -0.09 mmol/L (95% CI: -0.15, -0.03 mmol/L; P < 0.01) and -0.30% (95% CI: -0.37, -0.22%; P < 0.01), respectively. Further stratified analyses from high Jadad score studies showed that green tea significantly reduced fasting insulin concentrations (-1.16 μIU/mL; 95% CI: -1.91, -0.40 μIU/mL; P = 0.03).
  
  
  CONCLUSIONS
  This meta-analysis suggested that green tea had favorable effects, ie, decreased fasting glucose and Hb A1c concentrations. Subgroup analyses showed a significant reduction in fasting insulin concentrations in trials with high Jadad scores.
authors.affiliation: Research Center for Nutrition and Food Safety, Institute of Military Preventive Medicine, Third Military Medical University, Chongqing Key Laboratory of Nutrition and Food Safety, Chongqing Medical Nutrition Research Center, Chongqing, People's Republic of China.
authors.forename: Kai
authors.initials: K
authors.lastname: Liu
authors.forename: Rui
authors.initials: R
authors.lastname: Zhou
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.forename: Ka
authors.initials: K
authors.lastname: Chen
authors.forename: Lin-Ying
authors.initials: LY
authors.lastname: Shi
authors.forename: Jun-Dong
authors.initials: JD
authors.lastname: Zhu
authors.forename: Man-Tian
authors.initials: MT
authors.lastname: Mi
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage*; D001786:Blood Glucose / Q000032:analysis* / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D016208:Databases, Factual; D005215:Fasting; D006442:Glycated Hemoglobin / Q000032:analysis / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D010936:Plant Extracts / Q000008:administration & dosage*; D016032:Randomized Controlled Trials as Topic; D013662:Tea / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007328:Insulin; D010936:Plant Extracts; D013662:Tea